Because complete removal of the spleen in man and experimental animals produces immunologic deficiencies rendering the host particularly sensitive to overwhelming infection, surgical alternatives to total splenectomy are desirable. Using the model of congenital spherocytic hemolytic anemia in the deer mouse (Peromyscus maniculatis), this proposal will examine and compare the short and long-term hematologic and immunologic response (survival after intravenous pneumococci and antibody production to intravenous particulate antigen) to partial splenectomy and splenic autotransplantation with the response to total splenectomy and sham operation in spherocytic mice and normal littermates. In this way, it will be determined whether or not partial splenectomy preserves sufficient splenic mass to enhance resistance to post-splenectomy sepsis yet permits long-term control of the underlying splenic hematologic dysfunction.